Category The World Around us

WHY IS GLASS SO USEFUL?

Glass is one of the world’s oldest man-made materials. It is made from sand that is heated, mixed with other materials, and then shaped as it cools. Glass is easily shaped, cheap to make and easy to recycle over and over again. It has a huge range of used from buildings and optical instruments to bottles and glasses. Modern communication systems rely heavily on fibre-optic cables, which are made from very fine glass fibres.

Glass is a non-crystalline, often transparent amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, optics, and optoelectronics. The most familiar, and historically the oldest, types of manufactured glass are “silicate glasses” based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide (CaO), also called lime, and several minor additives.

Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. Glass can be coloured by adding metal salts, and can also be painted and printed with vitreous enamels. These qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows.

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HOW IS IRON TURNED INTO STEEL?

Iron has been extracted from iron ore since around 1500BC. Most iron is now turned into steel because this is a much more flexible metal. Steel is made by removing more carbon from the iron and adding other metals, depending on the type of steel that is being produced. Steel is made in an oxygen furnace. Molten iron mixed with scrap steel k poured into a furnace and oxygen is blown over it. The oxygen mixes with the carbon and removes it in the form of carbon monoxide.

Steel is iron that has most of the impurities removed. Steel also has a consistent concentration of carbon throughout (0.5 to 1.5 percent). Impurities like silica, phosphorous and sulfur weaken steel tremendously, so they must be eliminated. The advantage of steel over iron is greatly improved strength.

The open-hearth furnace is one way to create steel from pig iron. The pig iron, limestone and iron ore go into an open-hearth furnace. It is heated to about 1,600 degrees F (871 degrees C). The limestone and ore form a slag that floats on the surface. Impurities, including carbon, are oxidized and float out of the iron into the slag. When the carbon content is right, you have carbon steel.

Another way to create steel from pig iron is the Bessemer process, which involves the oxidation of the impurities in the pig iron by blowing air through the molten iron in a Bessemer converter. The heat of oxidation raises the temperature and keeps the iron molten. As the air passes through the molten pig iron, impurities unite with the oxygen to form oxides. Carbon monoxide burns off and the other impurities form slag.

However, most modern steel plants use what’s called a basic oxygen furnace to create steel. The advantage is speed, as the process is roughly 10 times faster than the open-hearth furnace. In these furnaces, high-purity oxygen blows through the molten pig iron, lowering carbon, silicon, manganese and phosphorous levels. The addition of chemical cleaning agents called fluxes help to reduce the sulfur and phosphorous levels.

A variety of metals might be alloyed with the steel at this point to create different properties. For example, the addition of 10 to 30 percent chromium creates stainless steel, which is very resistant to rust. The addition of chromium and molybdenum creates chrome-moly steel, which is strong and light.

When you think about it, there are two accidents of nature that have made it much easier for human technology to advance and flourish. One is the huge availability of iron ore. The second is the accessibility of vast quantities of oil and coal to power the production of iron. Without iron and energy, we probably would not have gotten nearly as far as we have today.

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HOW DOES MINING FOR MINERALS AFFECT THE ENVIRONMENT?

Mining can create a number of environmental problems. In the search for useful minerals, other substances are often discarded in the landscape. If these substances are toxic and they enter the water supply, wildlife and people may be affected. Mining can also cause serious physical damage to a landscape.

Mining is the extraction of minerals and other geological materials of economic value from deposits on the Earth. Mining adversely affects the environment by inducing loss of biodiversity, soil erosion, and contamination of surface water, groundwater, and soil. Mining can also trigger the formation of sinkholes. The leakage of chemicals from mining sites can also have detrimental effects on the health of the population living at or around the mining site.

In some countries, mining companies are expected to adhere to rehabilitation and environmental codes to ensure that the area mined is eventually transformed back into its original state. However, violations of such rules are quite common.

Water Pollution

Mining also causes water pollution which includes metal contamination, increased sediment levels in streams, and acid mine drainage. Pollutants released from processing plants, tailing ponds, underground mines, waste-disposal areas, active or abandoned surface or haulage roads, etc., act as the top sources of water pollution. Sediments released through soil erosion cause siltation or the smothering of stream beds. It adversely impacts irrigation, swimming, fishing, domestic water supply, and other activities dependent on such water bodies. High concentrations of toxic chemicals in water bodies pose a survival threat to aquatic flora and fauna and terrestrial species dependent on them for food. The acidic water released from metal mines or coal mines also drains into surface water or seeps below ground to acidify groundwater. The loss of normal pH of water can have disastrous effects on life sustained by such water.

Damage to Land

The creation of landscape blots like open pits and piles of waste rocks due to mining operations can lead to the physical destruction of the land at the mining site. Such disruptions can contribute to the deterioration of the area’s flora and fauna. There is also a huge possibility that many of the surface features that were present before mining activities cannot be replaced after the process has ended. The removal of soil layers and deep underground digging can destabilize the ground which threatens the future of roads and buildings in the area. For example, lead ore mining in Galena, Kansas between 1980 and 1985 triggered about 500 subsidence collapse features that led to the abandonment of the mines in the area. The entire mining site was later restored between 1994 and1995.

A landscape affected by mining can take a long time to heal. Sometimes it never recovers. Remediation efforts do not always ensure that the biodiversity of the area is restored. Species might be lost permanently.

Some of the negative impacts that mining can have on the environment include the loss of biodiversity, soil erosion, the contamination of surface water, and the formation of sinkholes.

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WHAT ARE CERAMICS?

Ceramics are materials made from stony or earthy material taken from the ground. Some ceramics, such as pottery and bricks, are moulded into shape and then baked (fired) to make them set. Glass is a type of ceramic that is heated first and then moulded into shape. Some ceramic materials are able to with-stand very high temperatures and are used for specialist application in industry and engineering.

Ceramic materials are special because of their properties. They typically possess high melting points, low electrical and thermal conductivity values, and high compressive strengths. Also they are generally hard and brittle with very good chemical and thermal stability. Ceramic materials can be categorized as traditional ceramics and advanced ceramics. Ceramic materials like clay are categorized as traditional ceramics and normally they are made of clay, silica, and feldspar. As its name suggests, traditional ceramics are not supposed to meet rigid specific properties after their production, so cheap technologies are utilized for most of the production processes.

Ball clay, China clay, Feldspar, Silica, Dolomite, Talc, Calcite and Nepheline are the common materials used for most of the ceramic products. Each raw material contributes a certain property such as dry strength, plasticity, shrinkage, etc. to the ceramic body. Therefore, by careful selection of materials, desired properties are acquired for the final output. Powder preparation is a major consideration in the ceramic industry. Surface area, particle size and distribution, particle shape, density, etc. each have their own effect on production. Powder has to be prepared to meet required particle size, particle shape, and other requirements for a particular industry. Milling is done to get the desired particle size. Unlike in the, advanced ceramics industry the purity of ceramic powder is not an issue in traditional ceramics.

The traditional ceramics industry originated long ago. Even thousands of years ago it was a well-established practice in many parts of the world. Today there are many divisions of this industry. Pottery, tableware, sanitary ware, tiles, structural clay products, refractories, blocks, and electrical porcelain are some of the products of traditional ceramics.

Advanced ceramics are special type of ceramics used mainly for electrical, electronic, optical, and magnetic applications. This sector is different from traditional ceramics due to the fact that ceramic powder preparation is quite important. Advanced production techniques are employed to assure that the produced ceramic powders possess sufficient purity. Generally chemical reactions are used to produce the ceramic powder such as Sol-gel processing and liquid-gas reactions like NH3 gas and SiCl4 liquid to produce Si3N4. Many of these methods are very costly. Therefore, powder preparation is always a cost factor in the advanced ceramics industry.

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HOW ARE TREES USED TO MAKE PAPER?

Trees are made up of thousands of tiny fibres. The paper-making process extracts these fibres and arranges them in a crisscross pattern. Wood is broken up into small pieces and then chemically treated to break it down into fibres. Most paper is produced from softwood trees such as spruce and pine.

Making pulp

1 Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution of

sodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.

Beating

2 The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.

Pulp to paper

3 In order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.

The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.

Finishing

4 Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.

The paper may be further finished by passing through a vat of sizing material. It may also receive a coating, which is either brushed on or rolled on. Coating adds chemicals or pigments to the paper’s surface, supplementing the sizings and fillers from earlier in the process. Fine clay is often used as a coating. The paper may next be supercalendered, that is, run through extremely smooth calendar rollers, for a final time. Then the paper is cut to the desired size.

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HOW DOES INDUSTRY USE RAW MATERIALS?

Most of the world’s industry involves working with raw materials extracted from the earth. As well as fossil fuels, minerals such as salt, clay and sulphur, and metals including copper and iron ore are all extracted for industrial purposes. The extraction of such materials is described as primary industry; activities that convert them into other products are known as secondary industries.

Raw materials are used in a multitude of products. They can take many different forms. The kind of raw materials inventory a company needs will depend on the type of manufacturing they do. For manufacturing companies, raw materials inventory requires detailed budgeting and a special framework for accounting on the balance sheet and income statement.

In some cases, raw materials may be divided into two categories: direct and indirect. Whether a raw material is direct or indirect will influence where it is reported on the balance sheet and how it is expensed on the income statement.

Direct raw materials are materials that companies directly use in the manufacturing of a finished product, such as wood for a chair. Indirect raw materials are not part of the final product but are instead used comprehensively in the production process.

Indirect raw materials will be recorded as long-term assets. Within long-term assets, they can fall under several different categories including selling, general, and administrative or property, plant, and equipment. Long-term assets usually follow some depreciation schedule which allows the assets to be expensed over time and matched with revenue they help to produce. For indirect raw materials, depreciation timing will usually be shorter than other long-term assets like a building expensed over several years.

Direct raw materials are placed in current assets as discussed above. Direct raw materials are expensed on the income statement within cost of goods sold. Manufacturing companies must also take added steps over non-manufacturing companies to create more detailed expense reporting on costs of goods sold. Direct raw materials are typically considered variable costs since the amount used depends on the quantities being produced.

A manufacturer calculates the amount of direct raw materials it needs for specific periods to ensure there are no shortages. By closely tracking the amount of direct raw materials bought and used, an entity can reduce unnecessary inventory stock, potentially lower ordering costs, and reduce the risk of material obsolescence.

Raw materials may degrade in storage or become unusable in a product for various reasons. In this case, the company declares them obsolete. If this occurs, the company expenses the inventory as a debit to write-offs and credits the obsolete inventory to decrease assets.

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